Internal combustion engine
An internal combustion engine (ICE, or IC engine) is a heat engine in which fuel combustion takes place inside a combustion chamber that forms an integral part of the working fluid flow circuit. The expanding high-temperature, high-pressure gases produced by that combustion act directly on pistons, turbine blades, a rotor or a nozzle, converting chemical energy into kinetic energy. The majority of ICEs are used in mobile applications, making them the principal power source for cars, aircraft and boats.
The first modern internal combustion engine — the Otto engine — was designed in 1876 by German engineer Nicolaus Otto, establishing the compressed-charge, four-cycle layout that underpins most automotive engines to the present day.
| Category | Heat engine; internal combustion |
| Principal working mechanism | Pistons (piston engine), turbine blades (gas turbine), rotor (Wankel), nozzle (jet engine) |
| First modern ICE | Otto engine, designed 1876 by Nicolaus Otto |
| First commercial motor-vehicle production with ICE | Karl Benz, 1886 |
| Combustion mode | Intermittent (piston, Wankel) or continuous (gas turbine, jet, rocket) |
| Typical fuels | Gasoline, diesel, natural gas, ethanol, biodiesel, bioethanol, ETBE, hydrogen |
| Ignition types | Spark ignition (SI) and compression ignition (CI) |
| First liquid-fueled rocket launch | Robert Goddard, 1926 |
| First jet aircraft | Heinkel He 178, 1939 |
| Collective vehicle category | Internal-combustion-engine vehicles (ICEV) |
What is an internal combustion engine?
An internal combustion engine burns fuel together with an oxidizer — normally air — inside a combustion chamber that is built directly into the path of the working fluid. The high-temperature and high-pressure gases that result apply force to a moving component such as a piston, turbine blade, rotor or nozzle, pushing it across a distance and so generating mechanical work.
This distinguishes the ICE from an external combustion engine, such as a steam engine or Stirling engine, in which energy reaches the working fluid without that fluid coming into contact with combustion products. External combustion engines use working fluids such as air, hot water, pressurised water or liquid sodium heated by a boiler.
ICEs divide into two broad classes according to how combustion proceeds. Intermittent-combustion engines — the two-stroke, four-stroke and six-stroke piston types, together with the Wankel rotary — fire in discrete pulses. Continuous-combustion engines — gas turbines, jet engines and most rocket engines — maintain a steady burn.
Who invented the internal combustion engine, and when?
Development of the ICE spanned several decades and many contributors. In 1791 John Barber developed the gas turbine, and in 1794 both Thomas Mead and Robert Street filed patents for gas engines; Street's design was also the first to use liquid fuel. John Stevens built the first American internal combustion engine in 1798.
In 1807 the French brothers Nicéphore Niépce (later the inventor of photography) and Claude Niépce ran the Pyréolophore, a prototype engine using controlled dust explosions, which Napoleon Bonaparte's government patented. The same year, Swiss engineer François Isaac de Rivaz built a hydrogen-fuelled engine ignited by electric spark, and in 1808 fitted it to a primitive vehicle, creating what is recorded as the world's first internal-combustion-powered automobile.
Samuel Brown patented the first industrial application of an internal combustion engine in 1823. Italian inventors Eugenio Barsanti and Felice Matteucci received British patent No. 1655 from the Great Seal Patent Office in 1857 for an improved apparatus obtaining motive power from gases, having first gained certification in the UK in 1854; further patents followed in France, Belgium and Piedmont between 1857 and 1859. Belgian engineer Jean Joseph Etienne Lenoir produced a gas-fired ICE in 1860, and in 1864 Nicolaus Otto patented the first atmospheric gas engine.
American George Brayton invented the first commercial liquid-fuelled ICE in 1872. Otto then patented the compressed-charge, four-cycle engine in 1876, working alongside Gottlieb Daimler and Wilhelm Maybach. Karl Benz patented a reliable two-stroke gasoline engine in 1879, and by 1886 had begun the first commercial production of motor vehicles using an ICE, integrating a three-wheeled, four-cycle engine and chassis into a single unit. Rudolf Diesel developed the first compressed-charge, compression-ignition engine in 1892. Robert Goddard launched the first liquid-fuelled rocket in 1926, and in 1939 the Heinkel He 178 became the world's first jet aircraft.
How does an ICE convert fuel into motion?
Combustion releases chemical energy stored in a fuel, raising the temperature and pressure of the resulting gases. Those gases expand and push against a mechanical surface — most commonly a piston inside a cylinder — causing linear or rotary movement. That movement is ultimately transmitted to wheels, propellers or other output devices.
In a piston engine the cycle may be completed in two strokes or four strokes of the piston per combustion event; a six-stroke variant also exists. The Wankel rotary engine replaces the reciprocating piston with an eccentrically mounted rotor, while gas turbines and jet engines use the continuous flow of combustion gases past turbine blades or through a nozzle to generate thrust or shaft power.
Fuels and ignition types
Most ICEs run on hydrocarbon-based fuels: gasoline, diesel, natural gas and ethanol are the most common. Renewable alternatives include biodiesel, used in compression-ignition engines, and bioethanol or ETBE (ethyl tert-butyl ether) derived from bioethanol, used in spark-ignition engines. Renewable fuels are frequently blended with fossil fuels rather than used in pure form.
Hydrogen is used only rarely and can be sourced from either fossil fuels or renewable energy processes. The practical use of non-petroleum fuels in ICEs has a long history: as early as 1900, Rudolf Diesel, the inventor of the compression-ignition engine, ran his engines on peanut oil.
The two principal ignition methods correspond to two engine families. Spark-ignition (SI) engines use an electric spark to initiate combustion of a premixed air-fuel charge, as in most gasoline engines. Compression-ignition (CI) engines rely on the heat generated by compressing air to ignite fuel injected into the cylinder, as in diesel engines.
Applications in vehicles and transport
Reciprocating piston engines are the dominant power source for land and water transport, including automobiles, motorcycles, ships and — to a lesser extent — locomotives, most of which now use diesel engines. Wankel rotary engines have been used in selected automobiles, aircraft and motorcycles. Vehicles using any of these engine types are collectively described as internal-combustion-engine vehicles (ICEV).
Where a high power-to-weight ratio is required, the ICE appears in the form of combustion turbines or jet engines, most notably in aircraft. While stationary industrial applications also exist, mobile transport remains the dominant use case for ICEs across all categories.
Etymology: engine, motor and related terms
The word engine derives via Old French from the Latin ingenium, meaning ability or cleverness, and historically referred to any piece of machinery — a usage preserved in terms such as siege engine. The word motor comes from the Latin motor, meaning mover, and denotes any machine that produces mechanical power.
By convention, electric motors are not called engines, while combustion engines are routinely called motors. The exception in common usage is the railway locomotive operated by electricity, which is referred to as an electric engine. In the context of boating, an ICE installed within the hull is called an engine, whereas an ICE mounted on the transom is called a motor.
Frequently asked questions
What is the difference between an internal combustion engine and an external combustion engine?
In an internal combustion engine, the fuel burns inside the combustion chamber that is part of the working fluid circuit, so the working fluid is the combustion product itself. In an external combustion engine — such as a steam or Stirling engine — energy is transferred to a separate working fluid, such as water or air, which never contacts the combustion products. The practical consequence is that ICEs tend to be more compact and lighter for a given power output.
Who designed the first modern internal combustion engine?
The first modern internal combustion engine, known as the Otto engine, was designed in 1876 by German engineer Nicolaus Otto. Otto had earlier patented the first atmospheric gas engine in 1864. His 1876 work, carried out alongside Gottlieb Daimler and Wilhelm Maybach, produced the compressed-charge, four-cycle layout that became the template for most automotive engines.
What fuels can an internal combustion engine use?
ICEs are most commonly fuelled by hydrocarbons such as gasoline, diesel, natural gas and ethanol. Renewable options include biodiesel for compression-ignition engines and bioethanol or ETBE for spark-ignition engines; these are often blended with fossil fuels. Hydrogen is a further option, obtainable from either fossil or renewable sources, though it remains rarely used. Rudolf Diesel demonstrated the use of peanut oil as early as 1900.
What is the difference between spark ignition and compression ignition?
Spark-ignition (SI) engines fire an electric spark to ignite a premixed charge of air and fuel, an approach typical of gasoline engines. Compression-ignition (CI) engines compress air to a temperature high enough to ignite fuel injected directly into the cylinder, as in diesel engines. Bioethanol and ETBE are associated with SI engines, while biodiesel is used in CI engines.
When was the first internal combustion powered automobile built?
In 1808, Swiss engineer François Isaac de Rivaz fitted a hydrogen-fuelled, electrically sparked internal combustion engine — which he had invented in 1807 — to a primitive vehicle, producing what is recorded as the world's first internal combustion powered automobile. The first commercial production of motor vehicles with an ICE came later, begun by Karl Benz in 1886 with a three-wheeled design integrating a four-cycle engine and chassis into a single unit.
What is the Wankel engine?
The Wankel engine is a type of internal combustion engine that uses an eccentrically mounted rotor rather than reciprocating pistons to convert the pressure of combustion into rotary motion. It falls within the intermittent-combustion class of ICEs, alongside two-stroke and four-stroke piston engines. Wankel engines have been used in selected automobiles, aircraft and motorcycles.
Are jet engines and rocket engines types of internal combustion engine?
Yes. Jet engines and most rocket engines are classified as internal combustion engines because combustion occurs inside the engine itself and the resulting gases act directly on engine components or exit through a nozzle. They belong to the continuous-combustion class of ICE, alongside gas turbines. The first jet aircraft, the Heinkel He 178, flew in 1939, while Robert Goddard launched the first liquid-fuelled rocket in 1926.
Why are combustion engines sometimes called motors?
The word motor derives from the Latin for mover and denotes any machine producing mechanical power, so it applies accurately to combustion engines. By long-established convention, however, electric motors are not called engines, while combustion engines are routinely called motors. The terminological distinction also appears in boating, where a hull-mounted ICE is an engine but a transom-mounted ICE is a motor.
Sources
- Wikipedia: Internal combustion engine — Factual basis of this entry